20 September 2024

Costain Group PLC

On-market Share Buyback Programme of £10m - Completion of First Tranche
and Commencement of Second Tranche

Costain Group PLC ("Costain") announces that, in accordance with the terms of its on-market share buyback programme announced on 21 August 2024 (the "Buyback"), Panmure Liberum Limited completed the first tranche of £5m (excluding stamp duty and expenses) on 19 September 2024, with a total of 4,909,473 ordinary shares purchased for cancellation.  Accordingly, Investec Bank plc will now commence the second tranche of the Buyback of up to a maximum consideration of £5m (excluding stamp duty and expenses) with effect from today.  The second tranche of the Buyback will continue to be conducted as set out in our announcement of 21 August 2024.

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